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Avalanche Forecast

Archived

Dec 11th, 2020–Dec 12th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Glacier.

The recent storm snow has settled and started to bond but the variability of the persistent layer below means testing is needed before committing to a line

Weather Forecast

No new snow today, cloudy skies may clear in the afternoon while winds stay calm. Freezing level is due to rise to 1000m. Tomorrow will be similar with a bit more cloud, possible flurries and winds picking up from the west in the evening. Sunday night more snow is forecast with winds shifting to the SW

Snowpack Summary

30cm of storm snow buried a variety of surfaces on Monday; surface hoar up to 10mm is rounding in some areas, localized freezing rain formed a crust in others while sunny breaks formed a crust on steeper solar aspects. Below that several surface hoar crust layers exist in the upper snowpack and the Nov 5 crust is down between 1m and 1.5m

Avalanche Summary

Tuesday's storm brought a widespread avalanche cycle to all aspects and elevations. Avalanche control Tuesday gave results to size 3.5. Numerous loose dry avalanches released yesterday when the sun came out to sz 1.5 as well as 2 sz 2s in the highway corridor from N and S aspects

Confidence

The weather pattern is stable

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.